The largest turtle in the world is the Leatherback Sea Turtle (Dermochelys coriacea), a giant of the open ocean. This marine reptile holds the record among all turtle species and is the heaviest non-crocodilian reptile alive today. Its immense size allows it to thrive in diverse and challenging marine environments across the globe.
The Record Holder and Its Dimensions
The Leatherback Sea Turtle is significantly larger than all other living turtle species. Adults commonly reach a curved carapace length of 5.5 to 7 feet (1.7 to 2.2 meters). Average adult weights range from 550 to 1,540 pounds (250 to 700 kilograms).
The largest verified specimen recorded measured nearly 9 feet (3 meters) in length and weighed 2,016 pounds (914 kilograms). This scale differentiates the Leatherback from the largest freshwater turtles, such as the Alligator Snapping Turtle, which rarely exceeds 220 pounds.
Distinctive Anatomy and Physiology
The structure of the Leatherback’s shell is unlike any other sea turtle, giving rise to its common name. Instead of a hard, bony carapace fused to the skeleton, its shell is composed of thick, rubbery skin covering a mosaic of thousands of tiny, interlocking dermal bones called osteoderms. This flexible, leathery shell provides a hydrodynamic, teardrop shape, featuring seven prominent longitudinal ridges that enhance swimming efficiency. The flexible carapace also allows the turtle to withstand the extreme hydrostatic pressures encountered during deep dives.
This massive body size enables gigantothermy, a form of regional endothermy. Due to its large volume-to-surface-area ratio, the Leatherback loses body heat slowly, maintaining a core temperature warmer than the surrounding cold water. This ability is enhanced by a thick layer of insulating fat and a specialized counter-current heat exchange system in its flippers. This adaptation permits the Leatherback to forage in frigid, high-latitude waters inaccessible to other cold-blooded sea turtles.
Global Habitat and Migration Patterns
The Leatherback Sea Turtle possesses the widest global distribution of any reptile, inhabiting the Atlantic, Pacific, and Indian Oceans. Their habitat spans from tropical nesting beaches in the Caribbean and Southeast Asia to cold foraging grounds off the coasts of Canada and the northern Pacific. They are primarily pelagic, spending the vast majority of their lives in the open ocean.
These turtles undertake trans-oceanic migrations, traveling up to 10,000 miles annually between nesting sites and feeding areas. These journeys are driven by their diet, which consists almost exclusively of soft-bodied prey like jellyfish and tunicates. The Leatherback is an accomplished deep-diver, routinely reaching depths greater than 3,280 feet (1,000 meters) to find food. The deepest recorded dive for a marine reptile was a descent of over 4,400 feet (1,344 meters), demonstrating extraordinary tolerance for pressure and cold.
Threats to the World’s Largest Turtle
Despite its size, the Leatherback Sea Turtle is classified as Vulnerable globally, and several distinct populations, particularly in the Pacific, are listed as Critically Endangered. The primary threat comes from incidental capture in fishing gear, known as bycatch. Turtles often become entangled in longlines, gillnets, and trawls, leading to injury or drowning since they must surface to breathe.
Marine pollution poses another significant danger, as Leatherbacks frequently mistake floating plastic debris for their jellyfish prey. Ingesting this plastic can block their digestive tract, leading to starvation. Furthermore, the destruction and erosion of tropical nesting beaches due to coastal development and rising sea levels threaten the species’ reproductive success.